On Sun, 29 Jul 2012 16:13:03 +0200, Timon Gehr <timon.g...@gmx.ch> wrote:
On 07/28/2012 06:47 PM, Simen Kjaeraas wrote:
On Sat, 28 Jul 2012 18:17:14 +0200, Zhenya <zh...@list.ru> wrote:
Why do not D allow templates with more than one tuple
parameters,at the
same time that C++11 support it:
Well, Walter implemented type tuples with automatic flattening,
The lack of multiple tuple parameters is not caused by automatic
flattening.
However, if they are introduced, the respective templates may only
ever be instantiated by IFTI.
To fix this, there would maybe need to be a special syntax to separate
the tuple parameters in an explicit instantiation, eg.
[snip]
with(Test!(int,double,,float)){
[snip]
Of course, that feels a little bolt-on. The alternative would be to
accept that templates with multiple tuple parameters cannot be
instantiated explicitly.
Indeed it does. We would do well to adopt another symbol than the comma,
I think. I thought for a moment foo!((int, float), (string, char)) could
work, as the comma operator is not defined to work on types. THe problem
appears when one tries to do the same with values: foo!((2,3), (4,5))
would be interpreted as foo!(3,5). Conceivably, one could simply allow
this syntax for type tuples.
Anyway, what other syntaxes do we have with a comma-separated list
and something else? Oh, foreach.
foreach (i, e; range) {}
foo!(int, float; string, char);
That's clearer, I think. And probably the best we get without breaking
other syntaxen.
--
Simen
